It is well known in the art to extend and retract protective covers, such as covers over swimming pools, with motor driven devices; and several United States Patents have issued for such devices. A good example of a device applied to swimming pools is the device taught by U.S. Pat. No. 4,811,433 issued to inventor Scott H. MacDonald et al on Mar. 14, 1989. The MacDonald invention includes, among other elements, a drum for rolling up a swimming pool cover, cables attached to the cover and passing through pulleys and guides for extending the cover, motor driven mechanism for driving the drum to roll up the cover and for driving reels to wrap the cables for extending the cover, and a special floppy clutch to cause the drive mechanism to engage the drum or the cable reels as needed to extend or roll up the cover. The drum and drive mechanism are housed in a recessed pit at one end of the pool, and there are guides and pulleys attached to the swimming pool structure to facilitate the operations. The device taught by MacDonald is typical of devices for rolling up and extending swimming pool covers.
A significant problem with the MacDonald invention and other known devices of the same nature is that the devices are quite complicated, and therefore expensive, and are relatively unreliable and subject to frequent adjustment and repair by reason of their complicated nature. Moreover, the drive and all associated mechanisms are permanent installations at the pool, and are continuously exposed to the pool water and chemicals, such as chlorine and acid, used in most swimming pools. This exposure creates further deterioration and maintenance problems.
Another problem with devices like the MacDonald device, is that the pool and surrounding area must be either originally designed and built to accommodate the cover and operating device, or must be extensively altered to accommodate such a device at a later date. A significant example of this expensive requirement is the enclosure pit formed into the pool deck at one end to accommodate the drive, floppy clutch, drum, and associated elements, such as taught in the MacDonald patent described above. Most such devices require a housing of similar nature for the various components. The storage pit, drive, pulleys, and guides associated with such a device are certainly cumbersome, and might well be clumsy or even dangerous for swimmers.
Yet another difficulty is in the stationary nature of the drum and driving elements, which dictates that the cover has to be translated across the pool in some manner to be wrapped on the drum, or extended from the drum. If the drive were to translate, providing a roll up actions without dragging friction, less power would be required.
What is clearly needed is a device for rolling up and unrolling protective covers over areas needing such protection, such as swimming pools or sports playing fields, with completely enclosed and translatable drive, so that the drum translates to roll up and unroll the cover, and the drive and associated mechanisms are enclosed in the drum. Such a device would be less expensive that conventional devices, both in manufacture and installation, and would be more durable in operation. Moreover, such a device would not present inconvenience or hazard to users of the pool or other area so protected, and could be conveniently stored away from the active area when not in use. Such a device could also be applied to any existing area or pool without alteration to the existing structure, and would therefore have broad application.